aes_ctr.c

/* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- *//* ==================================================================== * Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. All advertising materials mentioning features or use of this * software must display the following acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" * * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to * endorse or promote products derived from this software without * prior written permission. For written permission, please contact * openssl-core@openssl.org. * * 5. Products derived from this software may not be called "OpenSSL" * nor may "OpenSSL" appear in their names without prior written * permission of the OpenSSL Project. * * 6. Redistributions of any form whatsoever must retain the following * acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit (http://www.openssl.org/)" * * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. * ==================================================================== * */#ifndef AES_DEBUG# ifndef NDEBUG# define NDEBUG# endif#endif#include <assert.h>#include <openssl/aes.h>#include "aes_locl.h"/* NOTE: the IV/counter CTR mode is big-endian. The rest of the AES code * is endian-neutral. *//* increment counter (128-bit int) by 1 */staticvoid AES_ctr128_inc(unsignedchar *counter) {
unsignedlong c;
/* Grab bottom dword of counter and increment */
c = GETU32(counter + 12);
c++; c &= 0xFFFFFFFF;
PUTU32(counter + 12, c);
/* if no overflow, we're done */if (c)
return;
/* Grab 1st dword of counter and increment */
c = GETU32(counter + 8);
c++; c &= 0xFFFFFFFF;
PUTU32(counter + 8, c);
/* if no overflow, we're done */if (c)
return;
/* Grab 2nd dword of counter and increment */
c = GETU32(counter + 4);
c++; c &= 0xFFFFFFFF;
PUTU32(counter + 4, c);
/* if no overflow, we're done */if (c)
return;
/* Grab top dword of counter and increment */
c = GETU32(counter + 0);
c++; c &= 0xFFFFFFFF;
PUTU32(counter + 0, c);
}
/* The input encrypted as though 128bit counter mode is being * used. The extra state information to record how much of the * 128bit block we have used is contained in *num, and the * encrypted counter is kept in ecount_buf. Both *num and * ecount_buf must be initialised with zeros before the first * call to AES_ctr128_encrypt(). * * This algorithm assumes that the counter is in the x lower bits * of the IV (ivec), and that the application has full control over * overflow and the rest of the IV. This implementation takes NO * responsability for checking that the counter doesn't overflow * into the rest of the IV when incremented. */void AES_ctr128_encrypt(constunsignedchar *in, unsignedchar *out,
constunsignedlong length, const AES_KEY *key,
unsignedchar ivec[AES_BLOCK_SIZE],
unsignedchar ecount_buf[AES_BLOCK_SIZE],
unsignedint *num) {
unsignedint n;
unsignedlong l=length;
assert(in && out && key && counter && num);
assert(*num < AES_BLOCK_SIZE);
n = *num;
while (l--) {
if (n == 0) {
AES_encrypt(ivec, ecount_buf, key);
AES_ctr128_inc(ivec);
}
*(out++) = *(in++) ^ ecount_buf[n];
n = (n+1) % AES_BLOCK_SIZE;
}
*num=n;
}